“Rep. King’s amendment aims to block state laws protecting farm animals,” they wrote in the letter. “The provision is so broad and overreaching that it could also preempt a wide swath of state laws covering everything from child labor to dangerous pesticides to labeling of farm-raised fish to alcohol and tobacco products.”

The provision would prevent state and local governments from imposing regulations on agricultural goods produced in another state if the state or federal government has its own rules.

“In other words, if any one state in the union tolerates the production or sale of a particular agricultural product, under the King amendment the other 49 must do so as well,” the groups wrote.

King has supported the measure as a way to prevent states from “entering into trade protectionism” and allowing states to create a “patchwork” of laws “aimed at slowly suffocating production agriculture out of existence.”

But the organizations accuse that of being a handout to big agricultural companies.